STRUCTURAL STEEL Material Capacity FABRICATION 48 (1219 4 ...
Structural Steel Design Fabrication and Construction 00
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Transcript of Structural Steel Design Fabrication and Construction 00
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Structural Steel Design,Fabrication, and Construction
Jamie F. Farris, P.E.TxDOT Bridge Division
October 11, 2011
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Design
Fabrication
Construction
NSBA/AASHTO
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Bridge Design Manual - LRFD
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TxDOT Preferred Practices
TxDOT
FHWA Consultants
Academics
Fabricators Detailers
Steel Mill reps
Texas Steel
Quality Council
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Material Selection
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Unpainted Weathering Steel Preferred
A 709 Grades 50W and HPS 70W
More economical
Consider location conditions before choosing
Use details to prevent concrete staining
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Prevent Concrete
Staining
Include drip tabs on
all girders
Additional options
Stainless steel trays
Paint area over Bent
Weathering Steel
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Painted Steel
System IV noncoastal newconstruction
System III coastalnew construction
More info - See Item446 of TxDOT SpecBook
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Span Configuration & Geometry
3 and 4 span continuous Preferred
Interior Spans 20-30% longer then End Spans
Check uplift at the ends of continuous girders
Avoid high skews or major differentials wherepossible
L L1.2L to 1.3LInteriorExterior Exterior
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Girder Spacing I-girders
Limit CL-CL spa to 10 ft Min of 4 girders for vehicular bridge span
Tub girders Limit web spacing to 10 ft
Min of 3 girders for vehicular bridge span Consider use of PCPs for straight girders
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I-Shaped Plate Girders
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Geometric Constraints for
Straight Girders
Flange Width
D/4Flange Width 15 in
in Flange Thick 3 in
Web Thick in
0.25D
Min.
D
0.50 in
Min.
0.75 in Min.
3.00 in Max.
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Flange Width D/4
Flange Width 15 in
1 in Flange Thick 3 in
Web Thick in
0.25D
Min.
D
0.50 in
Min.
1.00 in Min.
3.00 in Max.
Geometric Constraints for
Curved Girders
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Flange Criteria
Flange Width
Constant
Transitions at field splices
Top = Bottom
Flange Thickness Use 10 ft min length
Use only a few sizes
In lieu of lateral bracing flange thickness
Use similar thicknesses
across girders
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Flange Criteria
Flange splices extend thicker flangesbeyond theoretical flange splice location
Theoretical Location
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Web Criteria
Web Depth
Whole inch increments
Dapped Ends: No more than 40% of web
depth
Do not use haunched webs
Web Thickness
Eliminate need for transverse stiffeners Discourage use of fully stiffened web
designs
Optimal designs have few sizes
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Web Criteria
Dont use Longitudinal stiffeners unlessweb depth > 120 in
Present
fabrication and
fatigue problems
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Field Splices
Show in plans as welded Offer bolted splice option
Locate at points of DL
contraflexure Girder field length ~ 130 ft max
Limit shipping width to 6 ft and
height to 9 ft Web splice locations at least
10 apart
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Bolted Field Splices
Galvanized bolts forpainted steel
1, 7/8, Dia
Class A surface
conditions Splice PL thickness
Add 1/8 tomin edge distancesin AASHTO LRFD
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Splice Fill Plates
Steel grade specified for girders not
available in thicknesses less than 3/8
Allow optional fill plate material (A 606, A
570, etc.)
Spec Book 447.4.B
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A325 vs. A490 Bolts
Contractors preferA325
A325 bolts can beretightened
A490 bolts aresensitive to tighteningprocedures
A490 bolts requireimpact wrenches thatmight not be available
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Max Spacing Straight = 30 ft
Curved = 20 ft
Provide at all endbearings
Straight - Set parallel
to skew up to 20o. Set
radial beyond 20o
Curved set radial to
girders
Diaphragms & X-Frames
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X-frame Half Pipe Stiffeners
Research Project0-5701
Gives girders
higher bucklingcapacities
Serves as abearing stiffener
Coming soon:Added to SGMDStandard
Skewed Bridges
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Lean On Bracing
Research Project 0-1772
Struts transfer forces to 1 or 2 X-frames
Minimize LL induced brace forces Reducing number of braces
Straight Bridges
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Stud Connectors
Full length of
girder
Min longitudinalSpa 4d
SGMD Standard
Not required ontop of flange splice
plates
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Bearings
Select from TxDOT
SGEB standard
Triple check bearing
seat elevations
Avoid costly HLMR,
disc, pot bearings
Bent Cap geometry
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Steel Tub Girders
Only use if this isthe best solution
Consider for long,
narrow, curved,bridges with tightradius
NSBA Practical
Steel Tub GirderDesign
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Tub Girders
Constant shape Rotated with x-slope
Top flange and Web
same requirements asI-girder
Avoid details more
critical than Cat. C
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Bottom Tension Flange
> thick
w/t 80
Classified as fracture-critical for 2-girder spans
All bottom flange edges
extend 2 in + beyondweb CL
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Inspection Access
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Slabbing and Stripping
Top View
Girder Elevation
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Multiple Head Cutting Bed -
Strips Out Flanges From
Wider Plates
Slabbing and Stripping
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Narrow Gap Electroslag Welding
Welding TimeApprox. =10- 20%
of multiple pass
weld
Minutes
versus
Hours
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Analyze girder system using grid analysis
Predict the behavior of girder system
once bridge is fully constructed
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Critical Stages of Stability
Girder Erection
Before concrete deck placement
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Research Study 0-5574
Curved Plate Girder Design for Safeand Economical Construction
Justify recommendations in PreferredPractices
Create uniformity among analyticalrequirements of curved I-girders during
early stages of construction
Girder erection and concrete slab
placement
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Field Monitoring Parametric Finite
Element Modeling
Survey of GirderErection Practices
PC Based
Analytical tools
Research Study 0-5574
Lifti P i t L ti
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Lifting Point Locations
Sh i I
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Shoring Issues
High costs
Prematureremoval
Site access issues
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UT Lift 1.1
ANALYTICAL TOOLS
Spreadsheet Behavior of girder
segments during
lifting Determines optimallift locations
Girderdeformations
Predicts girdertwist
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3D Finite Element
Program
Partially
constructed girdersystems
Staged deck
placementUT Bridge 1.5
ANALYTICAL TOOLS
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National Steel Bridge Alliance
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AASHTO/NSBA
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AASHTO/NSBA
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Guidelines for Steel
Girder Analysis Shop Detail Drawing
Review
Fabrication
Sample OwnersQuality AssuranceManual
Erection Guide Spec Coating Systems
Guide
AASHTO/NSBA
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AASHTO/NSBA
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Final published inEarly 2012
23 Chapters including Analysis
Load Combinations
Splice Design Substructure Design
Bearing Design
Deck Design
Design for Fatigue 7 Example Problems
A k l d t
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Acknowledgements
Brian Merrill, TxDOT BRG
John Holt, TxDOT BRG
Tom Schwerdt, TxDOT CST
Mike Hyzak, TxDOT BRG
Greg Turco, TxDOT BRGMichelle Romage-Chambers, TxDOT BRG
Todd Helwig, University of Texas
Karl Frank, Hirschfeld Industries
Jason Stith, Michael Baker, IncUniversity of Texas Researchers
TxDOT BRG Construction Section
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